This is a bizarre columnar Chalcanthite specimen that is coated by a thin layer of the iron sulfate romerite, through which nests of sharp, bladed melanterite crystals to 6 mm in size poke out every which way on all sides. Although not pristine (there are some damaged spots), it is dramatic and impressively displayable. According to museum records and the number on the back of the piece (19977), this dates to the time period as the Vaux expeditions of the 1920s and thus was most likely collected by Sam Gordon, then-curator, on one of the early Vaux expeditions (1st or 2nd) ! You can see this dating jives with the dating on the museum's own large format display label, noting Sam Gordon collected the specimen in 1921 (then on the Vaux expeditions) .